1. Technical Field
The present invention relates to an electronic timepiece and to a method of controlling an electronic timepiece that receives and acquires the current date and time from signals sent from GPS satellites or other positioning information satellites.
2. Related Art
GPS satellites with known orbits around the Earth are used in the GPS system, which can be used to determine one's position, and each GPS satellite carries an atomic clock. Each GPS satellite therefore also keeps extremely precise time information (also referred to as the GPS time or satellite time).
Because the satellite time does not account for leap seconds, however, UTC (Coordinated Universal Time) must be obtained by adding the accumulated leap seconds to the satellite time. Because the current leap second information is carried on page 18 of subframe 14 of the GPS satellite signal, the correct time can be set if this leap second information is also received.
Timekeeping devices having unit of using the time and leap second information contained in the navigation message received from such positioning information satellites to correct the leap second of the internal time kept by the timekeeping unit of the timekeeping device are known from the literature. See, for example, Japanese Unexamined Patent Appl. Pub. JP-A-2008-145287.
The timekeeping device described in JP-A-2008-145287 first acquires subframe and page identification information and time information from the navigation message sent from the GPS satellite. The time until leap second correction data is sent next is then calculated, and the receiving unit receives the navigation message at the time the leap second correction data can be received. The leap second value of the internal time data kept by the timekeeping unit is then corrected based on the leap second correction data contained in the received navigation message.
The timekeeping device taught in JP-A-2008-145287 also performs the reception operation when the reception operation is not needed and when signals cannot be received from the GPS satellites, however, and power consumption therefore rises. A problem that therefore results when the timekeeping device is a small portable device, such as a wristwatch, with small battery capacity is that the duration time is shortened.